Planographic plate and method of making the same



United States Patent PLAN OGRAPHIC PLATE AND METHOD MAKING THE SAME Douglas A. Newman, Sea Clitf, and Allan T. Schlotzliauer, Locust Valley, N. Y., assignors to Columbia Ribbon & Carbon Manufacturing Company, Inc., Glen Cove, N. Y., a corporation of New York No Drawing. Application November 6, 1948, Serial No. 58,786

16 Claims. (Cl. 101149.2)

This invention relatesto planographic printing plates and to the methods of making the same.

Relatively inexpensive planographic plates for use in instances where the number of copies desired is not too great have had increasingly favorable reception for the reason that better copies can be provided than is possible with alternate reproduction systems, for example, hectographic. The full acceptance of plates of this character, however, has been hampered by the fact that a plate which gives copies of the highest quality is somewhat too costly for most users, while a plate within an acceptable cost range has not been found which will give sufficiently good results to Warrant the change-over in the users equipment.

An object of the invention, therefore, is the production of a planographic plate capable of producing a reasonable number of copies of the foremost quality, and which can be made at a cost sufiiciently low to be attractive to users of duplicating equipment, and particularly those whose requirements as concerns numbers of copies are moderate.

Planographic plates of the type with which the invention is concerned normally have a base of a cellulosic material such as paper treated to give it high wet-strength and low wet-extensibility so as to withstand the moistening treatment and stresses undergone in the printing operation. Furthermore, the surface must have the appropriate hydrophilic-oleophilic balance to operate as a planographic plate.

Various treatments and coating compositions have been suggested in the past in an effort to provide a paper base plate which meets the above need, but none have been entirely successful for the reason that to produce plates capable of rendering acceptable copies, the numerous treatments to which they must be subjected bring the cost of the plate to a level where it cannot be used economically as a substitute for other duplication methods.

We have discovered, however, a coating solution which satisfies the exacting requirements for a planographic printing surface and which at the same time has additional properties which materially reduce the effort and expense required in the treatment of paper plates therewith, in addition to effecting other savings. The essential ingredient is a dibasic acid styrene copolymer, normally in the form of an ammonium or other alkali salt, and is marketed under the trade name Amberlite W-l, which expression is used hereinafter to designate compounds of this character. This material itself is inexpensive when compared with most materials which are in any way suitable for such coatings. Furthermore, when the same is incorporated in a coating solution insolubilized and dried, a tough, stable, rubber-like film is formed,

whereby plates coated therewith may be stored without deterioration. This coating is also found to have the proper balance between its hydrophilic and oleophilic properties, especially for plates which are to be used in work where long operating life is not the primary consideration.

Unlike most materials capable of providing films which lay the surface fibers of the paper and have suitable planographic properties, Amberlite W-l is suitable as a wetstrength sizing material for paper, and, in addition, has

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the property of being rendered insoluble by the action of heat at comparatively low temperatures.

The nature of the solution formed when Amberlite W-l is used as the film-forming constituent likewise has a marked effect upon the cost or' production in that more continuous films are obtainable with fewer treatments than when previously known planographic surfacing ma terials are used.

Other features and advantages will hereinafter appear.

A planographic plate or sheet of the character with which the invention is concerned normally consists of a base web of paper formed by the consolidation of suitable fibers using paper-making equipment of a known type. During the process of manufacture, the fiber is mixed in the beaters with a sizing material, or the web when formed is impregnated with such sizing material, selected to impart wet-strength to the web and decrease the water penetration thereof. This is necessary in order that the finished plate, which is used by continuously wetting the same, will have sufficient strength to withstand the stresses imposed thereon by a printing press in operation with minimum damage or deterioration, and further, so that changes in size and shape of the sheet which would distort an image imprinted thereon to an unacceptable degree are avoided. A sized sheet of this character is then provided with one or more coatings of a material which will lay any surface fibers and provide a surface having the appropriate hydrophilic-oleophilic balance. it has become customary to use a plurality of superposed coatings for the purpose since it is known that imperfections such as fiber ends and pinholes, which seriously aifect the quality of work of which the sheet is capable by introducing objectionable background tone, are much more eitectively covered when several light coatings are used in place of a single heavy one. '1 he sheet must be SllDj6Ctd to a drying treatment after each sizing or coating and, depending upon the quality and properties desired, may be calendered one or more times.

. 'l be improved surface coating which includes Amberllte W-l as the essential constituent thereof is found to have important advantages over the other coatings now known L0 be usable I01 this purpose. while the planographic properties of this material are the equivalent of those or materials formerly in use, we have round that it also possesses remarkable covering properties, so that flaws in the nature of fiber ends and pinholes are elimimated to an acceptable degree with fewer coats and a consequent saving in production costs.

Not only is an "Amberlite W-l film having a thickness equal to that or a film formed of previously used materials, the full equivalent thereof with regard to covering properties, but an additional feature of this material makes t economically possible to apply heavier and denser coat- 1ngs n a single operation. the most practical and expedltious impregnation or coating of paper webs is con ducted using apparatus in the nature or a vat through which the web may be passed, for example, the size tub normally used in connection with paper making machlnery. Such an arrangement, however, is usable with coating baths of low vlscoslty only. bince the continuity ot the resulting film depends upon the concentration of the solution, and since solutions of higher concentration have increased viscosity, the application of planographic surfaces to a paper web using materials previously known has required either that several low viscosity applications be made in the size tub, or the more complicated equipment be used to handle the higher viscosity solutions. Amberlite W-l, however, has the advantage of being readily dispersible in water to form solutions of a comparatively high concentration at a relatively low viscosity. For example, solutions having a concentration substantially in excess of five per cent have a viscosity such that they can be readily handled in the size tub while concentrations of this order using other known planographic coating ingredients would be so viscous as to preclude effective application using this apparatus.

The wet-strength sizing treatment to which paper to be used as a planographic plate is subjected, normally employs a material such as melamine having desirable moisture-resistance. Such materials previously used for this tion such as the amount of filler and its particle size,

the degree and number of ctlendering or pressing treatments used, and the extent of insolubilization treatment,

to which the coatings are subjected. v

Thus, it will be seen that we have provided a planographic plate having a surface coating such that the same is suitable for making a moderate number of copies of exceptionally good quality and which can be produced at a cost which is less than any substantially equivalent plate heretofore known. Furthermore, the coating material used readily lends itself to the usual treatments for modifying its properties in any desired manner, and is also capable of being applied to a base sheet after the image has been formed thereon to impart thereto the properties necessary for its use as a planographic plate.

In addition, the invention is seen to include the process,

of forming a planographic plate wherein the material used to impregnate and coat the base so affects the process steps required that a planographic plate which is the equivalent of those previously used can be produced in a more expeditious and less complicated manner.

Variations and modifications may be made within the scope of this invention and portions of the improvements may be used without others.

We claim:

1. A planographic plate comprising a base having a coating essentially of a dibasic acid styrene copolymer; and an ink receptive, water repellent image formed on said coating.

2. A planographic plate comprising a cellulosic base having a coating essentially of a water-insoluble dibasic acid styrene copolymer; and an ink-receptive, water-repellent image formed on said coating.

3. A planographic plate comprising a cellulosic base impregnated with a wet-strength sizing and having a surface coating, said sizing and coating each being essentially of a dibasic acid styrene copolymer; and an inkreceptive, water-repellent image formed on said surface coating.

4. A planographic plate comprising a base having a coating essentially of a dibasic acid styrene copolymer in the form of a salt; and an ink-receptive, water-repellent image formed on said coating.

5. A planographic plate as defined in claim 4 in which said salt is in the form of an ammonium salt.

6. A planographic plate comprising a cellulosic base impregnated with a Wet-strength sizing and having a surface coating, said sizing and coating each being essentially of a dibasic acid styrene copolymer in the form of a salt; and an ink-receptive, water-repellent image formed on said surface coating.

7. A planographic plate comprising a cellulosic base impregnated with a wet-strength sizing and a surface coating, the latter being essentially of a dibasic acid styrene copolymer; and an ink-receptive, water-repellent image formed on said surface coating.

8. A planographic plate comprising a cellulosic base impregnated with a wet-strength sizing and a surface coating, the latter being essentially of a dibasic acid styrene copolymer in the form of a salt; and an ink-receptive, water-repellent image formed on said surface coating.

9. The process of making a planographic plate comprising the steps of coating a surface of a cellulosic base with a solution which is essentially an aqueous dispersion of an alkali salt of a dibasic acid styrene copolymer; insolubilizing the same; and forming an ink-receptive, water-repellent image on said coating.

10. The process of making a planographic plate comprising the steps of coating a surface of a cellulosic base with a solution which is essentially an aqueous dispersion of a dibasic acid styrene copolymer in the form of an ammonium salt; insolubilizing the same by subjecting the coating to a temperature of not over 100 C. for not over two minutes; and forming an ink-receptive, water-repellent image on said coating.

11. The process of making a planographic plate comprising the steps of impregnating the material of a cellulosic base with a wet-strength solution; thereafter coating a surface of said base with a planographic surface forming solution, each of said solutions being essentially an aqueous dispersion of a dibasic acid styrene copolymer in the form of an alkali salt; and forming an ink-re- 6 ceptive, water-repellent image on said planographic coated surface.

12. The process of making a planographic plate comprising the steps of impregnating the material of a cellulosic base with a wet-strength solution; thereafter applying a single coating only to a surface of said base using a planographic surface forming solution, each of said solutions being essentially an aqueous dispersion of a dibasic acid styrene copolymer in the form of an alkali salt; and forming an ink-receptive, water-repellent image on said planographic coated surface.

13. The process of making a planographic plate comprising the steps of impregnating the material of a cellulosic base with a solution which is essentially an aqueous dispersion of a dibasic acid styrene copolymer in the form of an ammonium salt; consolidating said material into a web, insolubilizing the impregnant by sub jecting the web to heat; applying a single coating only to a surface of said web using a solution which is essentially an aqueous dispersion of a dibasic acid styrene copolymer in the form of an alkali salt, and insolubilizing saidcoating; and forming an ink-repective, water-repellent image on said single coating.

14. The process of making a planographic plate comprising the steps of impregnating the material of a cellulosic base with a solution which is essentially an aqueous dispersion of a dibasic acid styrene copolymer in the form of an ammonium salt; consolidating said material into a web, insolubilizing the impregnant by subjecting the web to heat; applying a single coating only to a surface of said web using a solution which is essentially an aqueous dispersion of a dibasic acid styrene copolymer in the form of an ammonium salt, and insolubilizing said coa-ting by subjecting said coating to heat; and forming an ink-receptive, water-repellent image on said single coating.

15. The process of making a planographic plate comprising the steps of impregnating the material of a cellulosic base with a solution which is essentially an aqueous dispersion of a dibasic acid styrene copolymer in the form of an ammonium salt; consolidating said material into a web, insolubilizing the impregnant by subjecting the web to heat; applying a single coating only to a surface of said web using a solution which is essentially an aqueous dispersion of a dibasic acid styrene copolymer in the form of an alkali salt, and insolubilizing said coating by reacting the same with a metallic salt solution; and forming an ink-receptive, water-repellent image on said single coating.

16. The process of making a planographic plate which includes the steps of impregnating a cellulosic base material with a wet-strength sizing; thereafter passing the same through a vat coating process wherein the vat contains a solution which is essentially an aqueous dispersion of a dibasic acid styrene copolymer in the form of an alkali salt; and forming an ink-receptive, water-repellent image on said vat coating.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,293,293 Allison Feb. 4, 1919 1,759,956 Reed May 27, 1930 2,072,487 Snyder Mar. 2, 1937 2,078,535 Hagedorn et al. Apr. 27, 1937 2,154,219 Shepherd Apr. 11, 1939 2,186,946 Wood Jan. 16, 1940 2,230,981 Toland et al. Feb. 4, 1941 2,298,943 Howard Oct. 13, 1942 2,311,889 Toland Feb. 23, 1943 2,319,033 Bernstein et al May 11, 1943 2,356,879 Pense et al. Aug. 29, 1944 2,373,287 Bassist Apr. 10, 1945 2,391,620 Quarles Dec. 25, 1945 2,402,469 Toland et al. June 18, 1946 2,428,716 M-cGill Oct. 7, 1947 2,486,804 Seymour Nov. 1, 1949 2,542,784 Van Dusen Feb. 20, 1951 (Other references on following page) 7 7 OTHER REFERENCES Set. No. 397,138, Fikentscher et al. (A. :P. .C;) ;pubdished: May, 1 1,;1 v9 43.

Gollins ;ct.al.*Wet'Strength-;1?aper. BOYCE :Fublishing -Co., N. Y. Copypavailable inHScientific.Libi axy. -On1y 7 pages 34, 47 and 76 cited.

.18 Information Bulletin .372-An not ated Comprehensive 'jIiist 'i df-ITrIade :Names "of f Syn'thetics. "Research Assn; .Iof tB'ritiShr'Rfibber Mfrs. ""Copy "avail-able in Division *50. i'only'pag'elt l cited.

Paper Trade "Journal; "April '3, 1947, pages "49-56. (Cqpy in Scientific Libraryl) 

1. A PLANOGRAPHIC PLATE COMPRISING A BASE HAVING A COATING ESSENTIALLY OF A DIBASIC ACID STYRENE COPOLYMER; AND AN INK RECEPTIVE, WATER REPELLENT IMAGE FORMED ON SAID COATING. 